Hydraulic gear shift mechanism

ABSTRACT

A hydraulic gear shift mechanism for a bicycle having a positioning mechanism for controlling the motion of the piston of a master cylinder assembly is disclosed, wherein the master cylinder assembly is in communication with a slave cylinder for operation of a derailleur. The positioning mechanism preferably includes a pivot shaft spaced apart from the handlebar, a rotating member rotatable about the pivot shaft, a push mechanism for rotating the rotating member in a first direction and a return mechanism for rotating the rotating member in a second direction. In a more preferred embodiment of the invention, an adjuster piston is threadingly engaged with the master cylinder assembly for adjusting the initial position of the slave cylinder.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/079,799, filed on Mar. 11, 2005 now U.S. Pat. No. 7,137,314, which isa division of U.S. patent application Ser. No. 09/876,346, filed on Jun.7, 2001, now U.S. Pat. No. 7,032,475, each of which are incorporatedherein in their entireties by this reference.

FIELD OF THE INVENTION

The present invention relates generally to a shift control device for abicycle, and more particularly, to a hydraulically operated bicycle gearshift mechanism utilized in conjunction with multiple sprockets andderailleurs.

BACKGROUND OF THE INVENTION

In typical bicycle gear shift devices, a shift control cable transmitsthe force of an actuating member operable by a bicyclist, to aderailleur arranged adjacent to the sprockets. To protect the cable fromdamage caused by environmental conditions, such as dirt or moisture, asleeve is generally provided on the shift control cable. However, evenwhen utilizing a sleeve, portions of the shift control cable, such asthe portion of the cable between the end of the cable sleeve and thederailleur, remain exposed and are thus susceptible to damage. This isparticularly disadvantageous for the portions of the shift control cablethat are close enough to the road surface such that dirt and mud fromthe road surface can precipitate on the cable. Continued exposure to theroad condition causes dirt to accumulate on the shift control cable,which eventually impedes the motion of the cable in and out of the cablesleeve. As a result, the shifting mechanism may then be movable eitherby great force only or not at all.

Another disadvantage of the cable operated gear shift systems is thatthe shift control cable tends to stretch over a period of time and thusthe derailleur mechanism needs to be adjusted in order to effect propershifting of gears. Additionally, the cable frequently becomes rusted orworn and accordingly will break when a gear change is attempted.Installation and maintenance of the control shift cable is complicatedand requires the elimination of any kinks and bends in the cable thatcan result in additional frictional force between the cable and thesleeve.

To overcome the disadvantages of cable operated gear shift systems,hydraulically operated systems have been proposed. However, the problemwith the known hydraulic gear shift systems is that the mechanisms usedfor indexed shifting are less sophisticated and imprecise. Accordingly,it is desirable to provide a hydraulic gear shift mechanism having acontrol device that provides precise positioning for indexed shifting.

Another disadvantage of known hydraulically operated gear shift systemsis that if the system needs an adjustment, an end point adjustment istypically made at the slave cylinder assembly to adjust the initialposition of the slave piston. Given that the slave cylinder assembly islocated near the derailleur, it is inconvenient to a bicycle rider tomake an adjustment at that location. Accordingly, it is desirable toprovide an adjuster at a location that is easily accessible to therider.

SUMMARY OF THE PREFERRED EMBODIMENTS

In a first aspect of the present invention, a hydraulic gear shiftmechanism for a bicycle having a handle bar is provided. The gear shiftmechanism preferably comprises a lever, a positioning mechanism, amaster cylinder assembly, a slave cylinder assembly, a conduit conveyinga fluid between the master cylinder assembly and slave cylinderassembly, and a derailleur operatively connected to the slave cylinderassembly and movable in response to the actuation of the master cylinderassembly.

In a preferred embodiment, the positioning mechanism is actuatable bythe lever and has a bracket, a pivot shaft spaced apart from thehandlebar and fixedly secured to the bracket, a member, a pushmechanism, and a return mechanism. The member is preferably rotatable ina first direction and a second direction about the pivot shaft. The pushmechanism preferably comprises a first latch segment and a push pawlbiased toward the first latch segment and configured to cooperate withthe first latch segment to rotate the member in a first direction.

In another preferred embodiment, the master cylinder assembly isoperatively connected to the member of the positioning mechanism andalso preferably has a piston that is movable in a push direction whenthe member rotates in a first direction and is movable in a returndirection when the member rotates in a second direction.

In accordance with another aspect of the present invention, a hydraulicgear shift mechanism for a bicycle having a handlebar is provided,wherein the gear shift mechanism comprises a lever, a positioningmechanism, a master cylinder assembly, a slave cylinder assembly, aconduit conveying a fluid between the master cylinder assembly and theslave cylinder assembly, and a derailleur operatively connected to theslave cylinder assembly and movable in response to the actuation of themaster cylinder assembly. The positioning mechanism is preferablyactuatable by the lever. The master cylinder assembly preferably isoperatively connected to the positioning mechanism and more preferablyhas a primary piston and an adjuster piston.

In preferred embodiments, the master cylinder assembly comprises amaster chamber and an adjuster chamber, the primary piston is disposedin the master chamber, and the adjuster piston is disposed in theadjuster chamber. In other preferred embodiments, the adjuster pistonhas a depth in the adjuster chamber, the slave cylinder assemblyincludes a slave piston having an initial position, and the depth of theadjuster piston in the adjuster chamber may be varied to adjust theinitial position of the slave piston. In yet other preferredembodiments, the lever is operable in a first direction and a seconddirection and is biased in a neutral position between the first andsecond directions.

In further preferred embodiments, the positioning mechanism comprises abracket, a pivot shaft spaced apart from the handlebar and fixedlysecured to the bracket, and a member, rotatable in a first direction anda second direction about the pivot shaft such that the rotation of themember in the first direction moves the primary piston in a pushdirection and the rotation of the member in the second direction movesthe primary piston in a return direction.

In still other preferred embodiments, the positioning mechanism furthercomprises a push mechanism operatively connected to the member and areturn mechanism operatively connected to the member, such that theoperation of the push mechanism rotates the member in the firstdirection, and the operation of the return mechanism rotates the memberin the second direction. In yet further preferred embodiments, theconduit has a conduit volume and the adjuster piston is rotatablymovable to adjust the conduit volume.

Other objects, features and advantages of the present invention willbecome apparent to those skilled in the art from the following detaileddescription. It is to be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the present invention, are given by way of illustrationand not limitation. Many changes and modifications within the scope ofthe present invention may be made without departing from the spiritthereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more readily understood by referring to theaccompanying drawings in which:

FIG. 1 is a perspective front view of a preferred embodiment of theshift control device of the present invention as attached to a bicyclehandlebar;

FIG. 2 is an exploded perspective view of a preferred embodiment of thepositioning mechanism of the present invention;

FIG. 3 is a top cross-sectional view of the positioning mechanism of thepresent invention in a neutral position;

FIG. 4 is a side cross-sectional view of a preferred embodiment of themaster cylinder assembly of the present invention;

FIG. 5 is a perspective view of a preferred embodiment of the slavecylinder assembly of the present invention as attached to a derailleur;

FIGS. 6 a-6 e are top cross-sectional views of the positioning mechanismof the present invention in operation in an upshift direction; and

FIGS. 7 a-7 d are top cross-sectional views of the positioning mechanismof the present invention in operation in a downshift direction.

Like numerals refer to like parts throughout the several views of thedrawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a preferred embodiment of the shift control device 100 ofthe present invention as attached to a bicycle handlebar 200. In apreferred embodiment of the invention, the shift control device 100includes a bracket or base member 110, a master cylinder assembly 300and a positioning mechanism 400. The handlebar 200 is preferably aflat-bar type handlebar having a cylindrical body that extendssubstantially along a handlebar axis 210. The bracket 110 is secured tothe handlebar 200 of the bicycle preferably by a clamp band 120 and abolt and nut assembly 121. A fluid conduit 500 connects the mastercylinder assembly 300 to the slave cylinder assembly, as will bediscussed in further detail below.

The positioning mechanism 400 preferably includes a lever 405 that, asdescribed in further detail below, controls the operation of thepositioning mechanism 400. In a preferred embodiment of the invention,the lever 405 is configured such that operation of the lever 405 in afirst direction, P, operates the positioning mechanism in a pushdirection, and in a second direction, R, operates the positioningmechanism in a return direction. In a more preferred embodiment of theinvention, as shown in FIG. 1, the first direction, P, is the directionof movement of the lever 405 from a neutral position toward thehandlebar 200 of the bicycle and the second direction, R, is thedirection of movement of the lever 405 from a neutral position away fromthe handlebar 200.

FIGS. 2 and 3 depict a preferred embodiment of the positioning mechanism400 of the present invention. In a preferred embodiment, the positioningmechanism 400 includes a pivot shaft 410 fixedly attached to the bracket110 and extending upwardly therefrom. The pivot shaft 410 is preferablypress fitted perpendicularly into the bottom plane of the bracket 110,however, other known techniques for connecting the pivot shaft to thebracket can also be used. A pinion gear 420, spacer 430 and latch plate440 are rotatably supported on the pivot shaft 410 and fixed to eachother. The pinion gear 420, spacer 430 and latch plate 440 arepreferably biased in a clockwise direction by spring S1.

A rack gear 450 is preferably slidably supported in a rail 111 of thebracket 110. Lid plate 451 is positioned above the rack gear 450 andsecured to the bracket 110 to slidably hold the rack gear 450 in place.The lid plate 451 is preferably secured to the bracket 110 with screws453, however, other known fasteners can also be used. The rack gear 450includes a plurality of gear teeth 452 which are dimensioned to engagethe pinion gear 420. Through the engagement of the pinion gear with thegear teeth 452 of the rack gear 450, the rotation of the pinion gear 420is translated to an axial movement of the rack gear 450. As best shownin FIG. 3, the rack gear 450 is connected to the piston rod 322 of themaster cylinder assembly 300. The axial movement of the rack gear 450results in a corresponding movement of the piston rod 322 of the mastercylinder assembly 300.

Referring to FIGS. 2 and 3, the positioning mechanism 400 preferablyincludes a fixed plate 480 and an operating plate 490. In a preferredembodiment of the invention, the fixed plate 480 is fixed to the bracket110 and an upper support 481 is fixedly coupled to the fixed plate 480.The operating plate 490 is rotatably supported on the main pivot shaft410 and biased in a neutral position by spring S4. The lever 405 ispreferably integral with the operating plate 490 such that the lever 405and operating plate 490 rotate together about the pivot shaft 410 whenthe lever 405 is operated.

To control the rotation of the latch plate 440, the positioningmechanism 400 includes a return pawl 460 and a push pawl 470 configuredto engage latch plate 440. The return pawl 460 is rotatably supported onpivot shaft 461 and includes an abutment 462, a first claw 463 and asecond claw 464. The pivot shaft 461 is fixedly attached to the bracket110. The return pawl 460 is preferably biased in a counterclockwisedirection by spring S2. The push pawl 470 is rotatably supported onpivot shaft 471 and biased toward in the counterclockwise direction byspring S3. Pivot shaft 471 is preferably fixed to the operating plat490. A nut 482 and washer 483 are threaded onto the pivot shaft 410 tosecure the components of the positioning mechanism 400 on the pivotshaft 410.

FIG. 4 depicts a preferred embodiment of the master cylinder assembly300 of the present invention. The master cylinder assembly 300 ispreferably rigidly coupled to bracket 110. In a preferred embodiment,the master cylinder assembly 300 includes a main chamber 311, a bleedport 313, an adjusting chamber 314 and a connecting port 312. A masterpiston 320 is disposed in the main chamber 311 and is sealed with arubber ring 321. A main chamber plug 315 is threaded into the mainchamber 311 for sealing the main chamber 311 and slidably supportingpiston rod 322. Piston rod 322 is preferably separable from the piston320. A bleed nipple 340 preferably plugs the bleed port 313.

An adjusting piston 330 is disposed in the adjusting chamber 314 and issealed with a rubber ring 331. An adjusting chamber plug 316 is threadedinto the adjusting chamber 314 for sealing the adjusting chamber 314 andsupporting the adjusting piston rod 332. The adjusting piston rod 332 ispreferably externally threaded, having threads that correspond to andengage with internal threads of the adjusting chamber plug 316. Theadjusting piston rod 332 is preferably connected to the adjusting piston330 such that the threading of the piston rod 332 into or out of theadjusting chamber plug 316 changes the location of the adjusting piston330 in the adjusting chamber 314.

The master cylinder assembly 300 and slave cylinder assembly 700 are influid communication via the fluid conduit 500. The fluid conduit 500 ispreferably connected to the master cylinder 300 at the connecting port312. Because the master cylinder assembly 300 and slave cylinderassembly 700 are in fluid communication, the initial position of theslave piston may be adjusted by changing the position of the adjustingpiston 330 in the adjusting chamber 314. For example, if the adjustingpiston 330 is threaded further into the adjusting chamber 314, the fluidis moved through the conduit 500 toward the slave cylinder assembly 700causing the slave piston to be pushed back. One of the advantages of thepresent invention is that the end point adjustment of the slave pistoncan be made conveniently at the handlebar.

As shown in FIG. 5, in a preferred embodiment of the invention, the gearshift mechanism includes a four-bar linkage type derailleur 600 having abase member 610, a shifting member 640, an outer link 620 and an innerlink 630. The base member is fixedly mountable on the bicycle frame andthe shifting member 640 is connected to the base member 610 via theouter link 620 and inner link 630. The shifting member 640 is preferablybiased toward the center line of the bicycle by a spring disposed insideof the four-bar linkage (not shown). A pulley cage 650, pivotablyconnected to the shifting member 640, rotatably supports a guide pulley651 and a tension pulley 652.

A slave cylinder assembly 700 is operatively connected to the derailleur600. In a preferred embodiment of the invention, the first end 701 ofthe slave cylinder assembly 700 is pivotably supported on the basemember 610 and the second end 702 of the slave cylinder assembly 700 ispivotably supported on the arm 621 formed on the outer link 620. Theslave cylinder assembly 700 preferably includes a slave cylinder chamber710. The fluid conduit 500 is preferably connected to the slave cylinderassembly 700 at the connecting port 711. A slave piston 720 is disposedin the slave cylinder chamber 710 and is sealed with a rubber ring 721.A slave cylinder plug 713 sealingly engages the slave cylinder chamber710 and slidingly supports the slave piston rod 730. Slave piston rod730 is preferably separable from piston 720 and is not rigidly connectedthereto.

FIG. 3 depicts the positioning mechanism 400 of the present invention ina neutral position. In the neutral state, the operating plate 490remains stationary because the spring S4 squeezes tab 491 formed on theoperating plate 490 and tab 486 formed on the fixed plate 480, as bestshown in FIG. 2, from both sides. In the neutral position, the push pawl470 rests on a ramp 484 peripherally formed on the fixed plate 480. Thefirst claw 463 of the return pawl 460 is engaged with positioning latchteeth 442 formed on the latch plate 440. The rack gear 450 is biased inthe direction away from the master cylinder assembly 300 (correspondingto the right in FIG. 3) by the biasing force of the return spring of thederailleur transmitted by fluid. The pinion gear 420 is biased in aclockwise direction by spring S1 and by the force transmitted from therack gear 450. The engagement of the first claw 463 of the return pawl460 with the positioning latch teeth 442 maintains the position of thepinion gear 420 and prevents the pinion gear 420 from freely rotating inthe clockwise direction.

FIGS. 6 a through 6 e depict the operation of the positioning mechanism400 in an upshift or push direction. To actuate the positioningmechanism 400 in a push direction, P, the lever 405 is activated in apush direction. As discussed above, in a preferred embodiment of theinvention, the push direction P is defined as the direction of movementof the lever 405 from the neutral position toward the handlebar. InFIGS. 6 a through 6 e, the elements that do not relate to the upshiftoperation are eliminated for ease of understanding.

FIG. 6 a depicts the positioning mechanism 400 of the present inventionin a neutral position. To push the piston rod 322, the operating plate490 is rotated in a counterclockwise or push direction. As best shown inFIG. 6 b, the rotation of the operating plate 490, causes the push pawl470 to slide off of the fixed plate ramp 484. Because the push pawl 470is biased toward the latch plate 440, the push pawl engages one of theteeth of the pushing latch 441. When the push pawl 470 has engaged oneof the teeth of the pushing latch 441, rotation of the operating plate490 translates to a rotation of the latch plate 440.

As best shown in FIG. 6 c, the rotation of the latch plate 440 driven bythe push pawl 470 causes the first claw 463 of the return pawl 460 todisengage from the positioning latch teeth 442. As the latch plate 440is further rotated, the return pawl 460 moves toward a tooth of thepositioning latch teeth adjacent the previously engaged tooth. Becausethe latch plate 440 is fixedly attached to the pinion gear 420, thepinion gear 420 rotates simultaneously with the latch plate 440 in thecounterclockwise direction. The rotation of the pinion gear 420 drivesthe rack gear 450 causing the piston rod 322 to further extend into themain chamber 311, thus displacing the fluid in the master cylinderassembly 300.

As best shown in FIG. 6 d, because the return pawl 460 is biased towardthe latch plate 440, the return pawl engages a tooth of the positioninglatch teeth 442 adjacent the previously engaged tooth. In a preferredembodiment of the invention, an audible click is produced when the firstclaw 463 of the return pawl 460 engages the positioning latch teeth 442.Moreover, the rider can feel the snap of the first claw 463 engaging thepositioning latch teeth 442. The audible click and the snapping motionalerts the rider that the first claw 463 of the return pawl 460 hasadvanced by one tooth completing one step of a multi-step shiftmechanism. Upon completion of the one step shift, the operating plate490 returns to the neutral position, as shown in FIG. 6 e.

In a preferred embodiment of the invention, the positioning mechanism400 of the present invention is configured to enable the rider to shiftmore than one step at a time, and more preferably to shift up to threesteps at a time. To perform a multi-step winding operation, the bicyclerider rotates the lever 405 further in the push direction P. Thepositioning mechanism 400 operates as described above in that the pushpawl 470 engages the pushing latch 441 driving the pushing latch in thepush direction P. The return pawl 460 disengages from the positioninglatch teeth 442 and engages the tooth adjacent the previously engagedtooth. However, in the multi-step operation, the bicycle rider continuesto rotate the lever 405 causing the latch plate 440 to rotate further,and the return pawl 460 to continue to engage neighboring teeth 442until the latch plate 440 ceases to rotate. In a preferred embodiment ofthe invention, the angle of rotation of the operating lever 405 in thepush direction P is limited by the contact of abutment 494 on theoperating plate 490 and protrusion 485 on the fixed plate 480.

FIGS. 7 a through 7 d depict the operation of the positioning mechanism400 in the return or downshift direction. To operate the positioningmechanism 400 in the return direction R, the lever 405 is rotated in thereturn or clockwise direction. As previously discussed, in a preferredembodiment of the invention, the release direction R is defined as thedirection of movement of the lever 405 from the neutral position awayfrom the handlebar. Elements that do not related to the downshiftoperation are eliminated from the figures for ease of understanding.

FIG. 7 a depicts the positioning mechanism 400 of the present inventionin a neutral position. Because the fluid in the fluid conduit 500 andthe master piston 320 are biased by spring S1 and by the return springof the derailleur 600 in the clockwise direction, the downshiftoperation can be performed by simply removing the force pushing on themaster piston rod 322. As best shown in FIG. 7 b, the rotation of theoperating plate 490 causes abutment 492 on the operating plate 490 tocontact abutment 462 on the return pawl 460. Abutment 462 is configuredsuch that contact with abutment 492 causes the first claw 463 of thereturn pawl 460 to disengage from the positioning latch 442. As thefirst claw 463 disengages from the positioning latch 442, the secondclaw 464 engages the positioning latch 442 to limit the rotation of thelatch plate 440 to one step, as shown in FIG. 7 c. In a preferredembodiment of the invention, return pawl 460 produces an audible clickwhen the second claw 464 engages the positioning latch 442. Moreover,the bicycle rider can feel the snap of the second claw 464 engaging thepositioning latch 442. The audible click and the snapping motion alertsthe rider that the return pawl 460 has advanced by one tooth. The ridercan then return the operating lever to its neutral position, completingone step of a multi-step shift mechanism.

The drawings depict a positioning mechanism for a nine step shiftoperation. However, the present invention is not limited to a nine stepshift operation and can be configured to vary the number of stepsavailable. Furthermore, the description of the positioning mechanism andthe corresponding drawings are directed to a positioning mechanism to beinstalled on the right hand side of a bicycle handlebar when viewed fromthe rider's perspective. The positioning mechanism installed on the lefthand side of the bicycle handlebar is substantially the mirror image ofthe positioning mechanism of the right hand side.

The embodiments described above are exemplary embodiments of a hydraulicgear shift mechanism. Those skilled in the art may now make numeroususes of, and departures from, the above-described embodiments withoutdeparting from the inventive concepts disclosed herein. Accordingly, thepresent invention is to be defined solely by the scope of the followingclaims.

1. A shift control device attachable to a handlebar of a bicycle foradjusting a slave piston of a slave cylinder assembly of a hydraulicgear shift mechanism, the shift control device comprising: a bracketattachable to the handlebar; a pivot shaft spaced apart from thehandlebar and fixedly secured to the bracket; a member rotatable in afirst direction and a second direction about the pivot shaft; a leveroperatively connected with the member, wherein the lever is biased in aneutral position and movable in a first and second direction, whereinthe neutral position is between the first and second directions, andwherein rotation of the member in the first direction moves the slavepiston in a push direction and the rotation of the member in the seconddirection moves the slave piston in a return direction.
 2. The shiftcontrol device of claim 1 further comprising a push mechanism configuredto cooperate with and rotate the member in the first direction; acooperate with and rotate the member in the first direction; a returnmechanism configured to cooperate with and rotate the member in thesecond direction; a master cylinder assembly having a master pistonoperatively connected to the member; and an adjusting piston adjustablyextending into the master cylinder assembly.
 3. The shift control deviceof claim 2, wherein the master cylinder assembly comprises a masterchamber and an adjuster chamber, the primary piston is disposed in themaster chamber, and the adjuster piston is disposed in the adjusterchamber.
 4. The shift control device of claim 2, wherein the pushmechanism comprises a first latch segment and a push pawl biased towardthe first latch segment and configured to cooperate with the first latchsegment to rotate the member in a first direction, and wherein thereturn mechanism comprises a second latch segment and a return pawl, thereturn pawl having a first claw and a second claw which alternatelyengage the second latch segment when the member is rotating in thesecond direction.
 5. The shift control device of claim 4 furthercomprising a pinion gear rotatable about the pivot shaft and operativelyconnected to the member wherein the pinion gear rotates with the member;and a rack gear engaged with the pinion gear and operatively connectedto the master piston of the master cylinder assembly, wherein therotation of the member in the first direction corresponds to a movementof the piston in a push direction and the rotation in the seconddirection corresponds to a movement of the piston in a return direction.6. The shift control device of claim 2 wherein the master cylinderassembly comprises a main chamber for the master piston and an adjusterchamber for the adjusting piston, the master piston is adjustable tovary the depth of the master cylinder in the master chamber, theadjusting piston is adjustable to vary the depth of the adjusting pistonin the adjuster chamber, and both the depth of the master piston in themaster chamber and the depth of the adjusting piston in the adjusterchamber define a volume of hydraulic fluid in the master cylinderassembly.
 7. The shift control device of claim 1 wherein the pivot shaftis substantially vertically oriented.
 8. A shift control deviceattachable to a handlebar of a bicycle for adjusting a slave piston of aslave cylinder assembly of a hydraulic shift gear mechanism, the shiftcontrol device comprising: a bracket attachable to the handlebar; apivot shaft spaced apart from the handlebar and fixedly secured to thebracket; a member rotatable in a first direction and a second directionabout the pivot shaft; a lever operatively connected with the member,wherein the lever is biased in a neutral position and movable in a firstand second direction, wherein the neutral position is between the firstand second directions, and wherein when the lever is moved away from theneutral position in one selected from the first direction and the seconddirection and then subsequently released, the lever returns to theneutral position.
 9. The shift control device of claim 8 furthercomprising a push mechanism configured to cooperate with and rotate themember in the first direction; a return mechanism configured tocooperate with and rotate the member in the second direction; a mastercylinder assembly having a master piston operatively connected to themember; and an adjusting piston adjustably extending into the mastercylinder assembly.
 10. The shift control device of claim 9, wherein themaster cylinder assembly comprises a master chamber and an adjusterchamber, the primary piston is disposed in the master chamber, and theadjuster piston is disposed in the adjuster chamber.
 11. The shiftcontrol device of claim 9, wherein the push mechanism comprises a firstlatch segment and a push pawl biased toward the first latch segment andconfigured to cooperate with the first latch segment to rotate themember in a first direction, and wherein the return mechanism comprisesa second latch segment and a return pawl, the return pawl having a firstclaw and a second claw which alternately engage the second latch segmentwhen the member is rotating in the second direction.
 12. The shiftcontrol device of claim 11 further comprising a pinion gear rotatableabout the pivot shaft and operatively connected to the member whereinthe pinion gear rotates with the member; and a rack gear engaged withthe pinion gear and operatively connected to the master piston of themaster cylinder assembly, wherein the rotation of the member in thefirst direction corresponds to a movement of the piston in a pushdirection and the rotation in the second direction corresponds to amovement of the piston in a return direction.
 13. The shift controldevice of claim 9 wherein the master cylinder assembly comprises a mainchamber for the master piston and an adjuster chamber for the adjustingpiston, the master piston is adjustable to vary the depth of the mastercylinder in the master chamber, the adjusting piston is adjustable tovary the depth of the adjusting piston in the adjuster chamber, and boththe depth of the master piston in the master chamber and the depth ofthe adjusting piston in the adjuster chamber define a volume ofhydraulic fluid in the master cylinder assembly.